In medicine, stents, or implants in general, are used for keeping vessels (especially: blood vessels) or tubes (especially trachea, esophagus, stomach, intestine, urethra, ureter) open. They are inserted or advanced, respectively, to the implantation site in a folded or collapsed, respectively, or crimped manner by using a catheter. At this site, the unfolding or decollapsing, respectively, of folded or collapsed stents is effected by removing an outer sleeve, which is arranged over or about the folded or collapsed stent, by means of reset or restoring forces; or by means of a balloon arranged inside the stent, which expands the stent encircling or encompassing the balloon when being inflated or blown up, respectively. Usually, stents are made from bio-compatible steel. Once unfolded or decollapsed, respectively, or expanded, it is difficult or impossible to return the stent back to a reduced diameter. The latter is regularly important if a stent which is placed incorrectly in the target organ (vessel or another organ, see above) has been unfolded or expanded; a stent which has been expanded or unfolded at the wrong site can generally not be re-implanted without having the possibility to reduce its diameter.
It may be desirable to propose a catheter for returning an implant, in particular a stent, back to a reduced diameter after having unfolded and/or expanded the stent at the implantation site. In addition, an implant, in particular a stent, which is suited hereto shall be proposed. Furthermore, a set including a catheter and an implant shall be presented.